种植体-基台连接结构的有限元分析及计算机研磨基台的设计研究

【作者】 汤春波；

【导师】 陈宁；

【作者基本信息】 南京医科大学 ， 口腔医学， 2009， 博士

【摘要】 尽管种植义齿在临床使用中取得了很高的成功率,但是,早期和晚期失败的情况仍然不可避免。主要原因是由于应力集中导致种植义齿的过度负荷或感染引起。种植体系统无论从选择还是设计上,都应具备良好的生物力学特性,从而保障种植修复的远期成功率。种植体的形态、种植体长度、种植体/基台连接形式、上部结构的设计、材料的选择等诸多因素均会影响应力的分布。其中种植系统的选择是首先需要考虑,也是临床上比较容易控制的。目前,国内外市场上种植体系统种类繁多,各系统之间最大区别在于种植体-基台连接结构的不同,分析临床常用的不同种植体-基台连接结构在种植体周围骨组织的应力分布,揭示各种连接方式对种植体及周围骨组织的力学影响,从中寻找出最佳结构的基台与种植体的连接方式,对提高种植义齿的临床成功率有重要意义。已有文献对种植义齿结构生物力学传递特性的研究多为离散的或单因素的比较分析,对临床选择并不具有充分的指导意义。本研究采用有限元方法对国际市场上使用最广泛、较典型的七种种植体-基台连接方式进行分析比较,为临床医师提供选择参考;同时使用CAD/CAM技术自主设计开发国产种植体系统的计算机研磨基台,改善国产种植体系统种植体-基台连接的稳定性,实现个性化美学修复的目的,并采用有限元方法分析比较传统角度基台和计算机研磨基台应力分布差异,为国产种植义齿的设计及改进提供理论与实验依据。实验一基于逆向工程的种植体系统精确建模实物种植体的数字化建模是种植系统有限元分析的重要基础。本研究综合利用三维光栅投影光学测量种植体曲面数据与平面影像测量细节特征相结合的方法,有效获取种植体点云数据。采用基于点云数据的数据处理、区域分析、特征拟合、形态建模的方法,完成七种典型种植体系统实物的精确建模。实验二种植体-基台连接结构的有限元分析运用ABAQUS软件对已建好的七种国际著名种植体系统种植体-基台连接结构进行有限元分析,对不同连接方式的种植体-基台模型施加相同的实验条件,得到五种垂直、五种水平、五种周期载荷下,七种连接方式的种植体-基台界面的应力分布情况。得出如下结论1.莫氏锥度连接种植体系统种植体-基台连接处应力集中,但基台螺丝应力很小。2.莫氏锥度式平台转移种植体系统(Ankylos)种植体及基台应力水平高于双六角12边式平台转移种植体系统(3i)。3.外六角连接紧固螺丝应力集中,易折断。内六角内圆锥混合式紧固螺丝连接应力水平较内八角、内三瓣、内六角低。4.内三瓣式连接种植体凹陷处及基台的三个凸轮处应力集中。5.水平载荷作用下种植体-基台连接各部件的应力显著增大,应尽量减少种植义齿的水平载荷。实验三种植体-基台整体在齿槽骨内的有限元应力分析建立了七种不同结构的种植体系统骨模型,施加递增的五种垂直载荷、五种水平载荷、五种周期性载荷,使用ABAQUS软件进行有限元分析,得到七种不同连接方式的种植体-基台整体在颌骨中的应力分布情况,进行比较分析,得出如下结论:1.非轴向载荷对种植体周围骨组织应力分布影响显著。2. Anklos,3i种植体系统可以减低种植体周围骨组织的应力集中,有利于种植体周围支持骨的保存,延长种植体的使用寿命。3. Bego内六角内圆锥混合式结构优于外六角、内三瓣、内六角及内八角结构。实验四计算机研磨基台数字化设计研究采用数字化设计技术,测量获取患者的愈合基台数字模型,基于特征匹配技术定位种植体,通过提取患者邻牙、牙龈等形态特征,对基台的颈缘、角度、肩台进行个性化设计,完成一例患者的计算机研磨基台的设计过程。实验五计算机研磨基台和传统基台的有限元研究通过有限元法分析比较计算机研磨基台和常规20°角度基台的应力分布差异,发现计算机研磨基台应力均匀分布,能较好地抵抗侧向力和剪切力。综上所述,本研究在逆向工程精确建模的基础上,使用ABAQUS有限元分析软件,对国际上常用的七种典型种植体系统在15种载荷条件下进行分析比较,揭示各种连接方式对种植体及周围骨组织的力学影响,评判不同结构的优劣,为使用者提供选择参考。同时自主研发设计国产种植体系统的计算机研磨基台,改善国产种植体-基台连接稳定性,实现种植义齿个性化的美学修复。更多还原

【Abstract】 Given the high success rate of implant denture in clinical application, early and late failure is still unavoidable in some cases. The main causes can be attributed to excessive loading or infection resulted from concentration of stress. The implant system should be selected and designed to have good biomechanical properties, so as to ensure the long-term success rate of implant restorations. The stress distribution is subject to a number of factors, such as the implant shape and length, the implant/abutment connection types, the design of superstructure and the selection of materials. Among them, the selection of implant system should be taken into primary consideration, and is also relatively easy to be controlled clinically.At present, there are many implant systems on both domestic and overseas markets, and the greatest difference between them lies in the implant - abutment connection structures. It is of great significance to a higher clinical success rate of implant denture to analyze the stress distribution of different implant-abutment connection structures commonly used clinically in the bone tissues around the implant and to reveal the mechanical effect of different connection designs on the implant and the surrounding bone tissues, so as to find the optimum structure for abutment and implant connection forms. In the available literature, researches on the biomechanical transfer characteristics of implant denture structure are mostly of comparison and analysis of discrete or individual factors, and these results cannot provide full guide in the clinical selection.Experiment 1: Digital modeling for implant-abutment structures based on reverse engineeringDigital modeling for physical implants is an important basis for the FEM analysis of the implant systems. In this chapter, the point cloud data of the implants is obtained by an integrated method, which combines. the optical measurement of implant profile data by 3D optical grating projection with the plane-image measurement of characteristic details. Digital modeling for the seven typical physical implant systems is accomplished by using the method of data processing, region analysis, feature fitting and shape modeling based on the point cloud data.Experiment 2: FE stress analysis of implant-abutment connection typesThe ABAQUS was used to perform FE analysis of the models of the implant-abutment connection structures of the seven internationally known implant systems. Identical experiment conditions were applied for the implant-abutment models of different connections, to obtain the stress distribution at the implant-abutment interfaces of the seven models under five vertical loads, five horizontal loads and five cyclic loads. The following conclusions have been obtained:1. In the implant system with Morse taper connection, the stress is concentrated at the implant-abutment structure, but the stress on the abutment screw is very small.2. The stress level of the implant-abutment in the implant system with Morse taper platform transfer is higher than that of the implant system with dual-hexagon 12-side platform transfer.3. The fixation screw in an outer hexagon connection is subject to concentrated stress and is therefore likely to break. The stress level of mixed inner hexagon inner cone fixation screw is lower than that of the inner octagon, inner trivalve and inner hexagon types.4. Stress is concentrated at the implant recess and three cams of the abutment in the inner trivalve connection.5. Under the action of horizontal load, the stress in components of implant-abutment connection increases substantially, therefore the horizontal load to an implanted denture should be minimized. Experiment 3: FE stress analysis of implant-abutment assemblies in the alveolar bone Implant-bone models were established for seven different structures, and five vertical loads, five horizontal loads and five cyclic loads were applied in incremental magnitude. The ABAQUS software was used for FE analysis, to obtain the stress distribution of implant-abutment assemblies of seven different connections in the jaw bone. The following conclusions have been obtained after comparison and analysis:1. The non-axial loads produce significant effect on the stress distribution in the one tissues around the implant.2. The Anklos and 3i implant systems can reduce the stress concentration in the bone tissues around the implant, favoring the conservation of supporting bone around the implant and extending the service life of the implant.3. The Bego mixed inner hexagon and inner cone structure is superior to outer hexagon, inner trivalve, inner hexagon and inner octagon structures.Experiment 4: Digital design and experiment analysis for personalized abutment.The digital design technology was applied to measure and obtain the curing digital model of a patient. The implant was positioned based on the feature matching technique. The personalized design of the abutment neck edge, angle and shoulder of the patient are implemented by extracting the morphological characteristics of the corresponding adjacent teeth and gingiva. Finally, the CAD design process is completed for the personalized abutment of a patient.Experiment 5:Finite element study of Computer-milled abutment and custom abutment Finite element method was used to compare of difference in computer-milled abtment and custom abutment with 20°angle. The result showed that computer-milled abutment stress uniformly distributed and that can better resist the lateral force and the horizontal loadIn summary, with this research, analysis and comparison was performed for seven typical implant systems in common use internationally under 15 loading conditions, on the basis of reverse engineering and precise modeling and using the powerful ABAQUS FE analysis software, to reveal the mechanical effect of different connection forms on the implant and its surrounding bone tissues and evaluate the advantages and disadvantages of different structures, so as to provide reference for selection by users. In the meantime, a personalized abutment for the China-made implant system has been developed and designed by our own, to enable improving the stability of the China-made implant-abutment connection and realize personalized aesthetic repair of implant denture.更多还原